Various implantable medical devices have been clinically implanted or proposed for therapeutically treating or monitoring one or more physiological conditions of a patient. Such devices may be adapted to monitor or treat conditions or functions relating to heart, muscle, nerve, brain, stomach, endocrine organs or other organs and their related functions. Advances in design and manufacture of miniaturized electronic and sensing devices have enabled development of implantable devices capable of therapeutic as well as diagnostic functions such as pacemakers, cardioverters, defibrillators, biochemical sensors, and pressure sensors, among others. Such devices may be associated with leads for electrical functions or may be wireless, with the ability to transmit data electronically either to another device implanted in the patient or to another device located externally of the patient, or both.
Although implantation of some devices requires a surgical procedure (e.g., pacemakers, defibrillators, etc.) other devices may be small enough to be delivered and placed at an intended deployment site in a relatively noninvasive manner, such as by a percutaneous delivery catheter. Depending on the nature, function and intended deployment site of the device, the manner in which the device is fixed in place and oriented in the body may affect the operation and accuracy of the device. Consequently, the means by which the device is fixed in place in the body can be a significant factor in its performance and utility.
By way of illustrative example, implantable miniature sensors have been proposed and used in blood vessels to measure directly the diastolic, systolic and mean blood pressures, as well as body temperature and cardiac output. Such direct in vivo measurement of hemodynamic parameters may provide significant information to clinicians to facilitate diagnostic and therapeutic decisions. If linked electronically to another implanted therapeutic device (e.g., a pacemaker), the data can be used to facilitate control of that device. Such sensors also, or alternatively, may be wirelessly linked to an external receiver. As one example, patients with chronic cardiovascular conditions, particularly patients suffering from chronic heart failure, may benefit from the use of implantable sensors adapted to monitor blood pressures. Promising indications have been reported for using such implantable sensors. Accurate knowledge of a patient's hemodynamic parameters can inform the decision whether to admit the patient to the hospital or whether the patient's condition can be managed with other therapies not requiring hospital admission. This is particularly so in connection with measurements of the blood pressure in the pulmonary artery that cannot be measured readily from an external location. Assessing a patient's pulmonary artery blood pressure is a critical factor in diagnosing the heart failure patient and determining how best to manage the patient. Typically, blood pressure in the pulmonary artery has been determined by using a balloon-tipped pulmonary artery catheter having a pressure measurement function and sold under the trademark SWAN-GANZ, which is inserted and navigated through the right side of the patient's heart and the pulmonary valve into the pulmonary artery, a procedure that requires hospitalization. It has been estimated that there are about five million patients in the United States who suffer from heart failure with approximately one million hospital admissions per year to assess and treat the condition. It would be desirable to provide a means by which such data could be obtained before admitting the patient to the hospital as the patient may experience an improved quality of life and it might avoid the necessity for and cost of hospitalization.
It is among the general objects of the invention to provide a minimally invasive, improved means for controllably placing and supporting an implantable sensor within a body lumen in a position, location and sensor element orientation that facilitates the operation of the device, in which the means includes a fixation member to which the sensor is mounted to achieve these objects.